This research proposal will answer fundamental and critical questions in primate auditory neurophysiology. To investigate the issue of how auditory cortical neurons encode acoustic space, we propose to record neuronal activity in the primary (A1) and caudomedial (CM) cortical fields in the awake, behaving macaque monkey. These experiments allow direct comparison of neuronal response characteristics to the perception of sound source location in the same subjects. Monkeys will perform a go/no-go lever task to indicate the change in location of acoustic targets which vary in intensity. Stimuli will be presented from 360 degrees of azimuth and 240 in elevation, as well as intermediate locations. . Data from this laboratory indicate that individual neurons in A1 and CM are sensitive to the location of a sound source, and are modulated by varying sound intensities. However, the ability to accurately localize acoustic stimuli remains relatively constant across a small range of sound intensities. Therefore, the experiments of this proposal will correlate neuronal activity in both A1 and CM while monkeys perform the sound localization task to acoustic stimuli of varying intensities. Single and multi-unit data will be analyzed with respect to the overall firing rate using traditional methods, as well as a neural network approach. The results of this study will fill a major gap in the fundamental understanding of primate auditory cortex and may ultimately promote the quality of human life.